Too bad you've abandoned this project.
I bet there are still many people interested in buying this board.
I've ordered a couple of universal boards from China but they're still more than twice the size of the one you've designed. They're cheap though. You can get them for less than $25 shipped and they even come with a remote.
Anyway, not sure if I should revive this project or not.
On a technical note, I would replace the 328PA with a 328PB which I'm currently using for my new IN-16 clock - has more capabilities, and would be more stable with GPS communications.
Not sure if it would pay, though. Hard to compete with boards coming out of China. Also, not sure if I have enough time to support this project - I'm guessing there would need to be a lot more support for a board than a finished clock.
Why not just sell them without support?
I mean, I don't expect support for these Chinese boards either but I'm OK with that and I guess most people here are.
The Chinese boards don't even come with a manual.